bpf: Add bpf_get_attach_cookie() BPF helper to access bpf_cookie value

Add new BPF helper, bpf_get_attach_cookie(), which can be used by BPF programs
to get access to a user-provided bpf_cookie value, specified during BPF
program attachment (BPF link creation) time.

Naming is hard, though. With the concept being named "BPF cookie", I've
considered calling the helper:
  - bpf_get_cookie() -- seems too unspecific and easily mistaken with socket
    cookie;
  - bpf_get_bpf_cookie() -- too much tautology;
  - bpf_get_link_cookie() -- would be ok, but while we create a BPF link to
    attach BPF program to BPF hook, it's still an "attachment" and the
    bpf_cookie is associated with BPF program attachment to a hook, not a BPF
    link itself. Technically, we could support bpf_cookie with old-style
    cgroup programs.So I ultimately rejected it in favor of
    bpf_get_attach_cookie().

Currently all perf_event-backed BPF program types support
bpf_get_attach_cookie() helper. Follow-up patches will add support for
fentry/fexit programs as well.

While at it, mark bpf_tracing_func_proto() as static to make it obvious that
it's only used from within the kernel/trace/bpf_trace.c.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210815070609.987780-7-andrii@kernel.org

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 83c3cc5e90dfe022a93e7fe568f8a1e8914ab271..f4c16f19f83e3edcf11abb4541a538ef468d395a 100644 (file)
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2102,9 +2102,6 @@ extern const struct bpf_func_proto bpf_btf_find_by_name_kind_proto;
 extern const struct bpf_func_proto bpf_sk_setsockopt_proto;
 extern const struct bpf_func_proto bpf_sk_getsockopt_proto;
 
-const struct bpf_func_proto *bpf_tracing_func_proto(
-       enum bpf_func_id func_id, const struct bpf_prog *prog);
-
 const struct bpf_func_proto *tracing_prog_func_proto(
   enum bpf_func_id func_id, const struct bpf_prog *prog);
 

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 63ee482d50e17a219cf96a97444a02ccc52c402b..c4f7892edb2b31fe4918a85f371c0c1579eba837 100644 (file)
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4856,6 +4856,21 @@ union bpf_attr {
  *             Get address of the traced function (for tracing and kprobe programs).
  *     Return
  *             Address of the traced function.
+ *
+ * u64 bpf_get_attach_cookie(void *ctx)
+ *     Description
+ *             Get bpf_cookie value provided (optionally) during the program
+ *             attachment. It might be different for each individual
+ *             attachment, even if BPF program itself is the same.
+ *             Expects BPF program context *ctx* as a first argument.
+ *
+ *             Supported for the following program types:
+ *                     - kprobe/uprobe;
+ *                     - tracepoint;
+ *                     - perf_event.
+ *     Return
+ *             Value specified by user at BPF link creation/attachment time
+ *             or 0, if it was not specified.
  */
 #define __BPF_FUNC_MAPPER(FN)          \
        FN(unspec),                     \
@@ -5032,6 +5047,7 @@ union bpf_attr {
        FN(timer_start),                \
        FN(timer_cancel),               \
        FN(get_func_ip),                \
+       FN(get_attach_cookie),          \
        /* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 57879d28f824e83a5b415cbfd82afa93967b5009..cbc73c08c4a4e70b5fef831bbf844b5a4356cfd8 100644 (file)
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -975,7 +975,34 @@ static const struct bpf_func_proto bpf_get_func_ip_proto_kprobe = {
        .arg1_type      = ARG_PTR_TO_CTX,
 };
 
-const struct bpf_func_proto *
+BPF_CALL_1(bpf_get_attach_cookie_trace, void *, ctx)
+{
+       struct bpf_trace_run_ctx *run_ctx;
+
+       run_ctx = container_of(current->bpf_ctx, struct bpf_trace_run_ctx, run_ctx);
+       return run_ctx->bpf_cookie;
+}
+
+static const struct bpf_func_proto bpf_get_attach_cookie_proto_trace = {
+       .func           = bpf_get_attach_cookie_trace,
+       .gpl_only       = false,
+       .ret_type       = RET_INTEGER,
+       .arg1_type      = ARG_PTR_TO_CTX,
+};
+
+BPF_CALL_1(bpf_get_attach_cookie_pe, struct bpf_perf_event_data_kern *, ctx)
+{
+       return ctx->event->bpf_cookie;
+}
+
+static const struct bpf_func_proto bpf_get_attach_cookie_proto_pe = {
+       .func           = bpf_get_attach_cookie_pe,
+       .gpl_only       = false,
+       .ret_type       = RET_INTEGER,
+       .arg1_type      = ARG_PTR_TO_CTX,
+};
+
+static const struct bpf_func_proto *
 bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 {
        switch (func_id) {
@@ -1109,6 +1136,8 @@ kprobe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 #endif
        case BPF_FUNC_get_func_ip:
                return &bpf_get_func_ip_proto_kprobe;
+       case BPF_FUNC_get_attach_cookie:
+               return &bpf_get_attach_cookie_proto_trace;
        default:
                return bpf_tracing_func_proto(func_id, prog);
        }
@@ -1219,6 +1248,8 @@ tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
                return &bpf_get_stackid_proto_tp;
        case BPF_FUNC_get_stack:
                return &bpf_get_stack_proto_tp;
+       case BPF_FUNC_get_attach_cookie:
+               return &bpf_get_attach_cookie_proto_trace;
        default:
                return bpf_tracing_func_proto(func_id, prog);
        }
@@ -1326,6 +1357,8 @@ pe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
                return &bpf_perf_prog_read_value_proto;
        case BPF_FUNC_read_branch_records:
                return &bpf_read_branch_records_proto;
+       case BPF_FUNC_get_attach_cookie:
+               return &bpf_get_attach_cookie_proto_pe;
        default:
                return bpf_tracing_func_proto(func_id, prog);
        }

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 63ee482d50e17a219cf96a97444a02ccc52c402b..c4f7892edb2b31fe4918a85f371c0c1579eba837 100644 (file)
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4856,6 +4856,21 @@ union bpf_attr {
  *             Get address of the traced function (for tracing and kprobe programs).
  *     Return
  *             Address of the traced function.
+ *
+ * u64 bpf_get_attach_cookie(void *ctx)
+ *     Description
+ *             Get bpf_cookie value provided (optionally) during the program
+ *             attachment. It might be different for each individual
+ *             attachment, even if BPF program itself is the same.
+ *             Expects BPF program context *ctx* as a first argument.
+ *
+ *             Supported for the following program types:
+ *                     - kprobe/uprobe;
+ *                     - tracepoint;
+ *                     - perf_event.
+ *     Return
+ *             Value specified by user at BPF link creation/attachment time
+ *             or 0, if it was not specified.
  */
 #define __BPF_FUNC_MAPPER(FN)          \
        FN(unspec),                     \
@@ -5032,6 +5047,7 @@ union bpf_attr {
        FN(timer_start),                \
        FN(timer_cancel),               \
        FN(get_func_ip),                \
+       FN(get_attach_cookie),          \
        /* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper